Recently, heat-shrinkable plastic films made from a variety of resins are widely used for applications such as external packaging for improving the appearance of packaged goods, packaging for avoiding direct collision of contents, and label packaging for both of a protection of glass bottles or plastic bottles and indication of commercial products. Among these heat-shrinkable plastic films, stretched films made from polyvinyl chloride resin, polystyrene resin, polyester resin, or the like are used for the purpose of labeling, cap sealing or assembling packaging in various containers such as polyethylene terephthalate (PET) containers, polyethylene containers, and glass containers. However, although excellent in shrinkage characteristics, polyvinyl chloride films pose problems of, in addition to low heat resistance, generating a hydrogen chloride gas during incineration, generating dioxins, and the like.
Therefore, polystyrene films, which do not pose a problem of generating dioxins during incineration, have been widely utilized as shrinkable labels. The amount of use of polystyrene films tends to increase as the distribution amount of PET containers increases. Further, general heat-shrinkable polystyrene films that are stretched at a high ratio in the width direction and greatly shrunk in the width direction (namely, heat-shrinkable polystyrene films whose main shrinkage direction is the width direction) are widely utilized (Patent Document 1).
Patent Document 1: Japanese Unexamined Patent Publication No. 2003-94520